Method of forming screw-receiving fasteners



Dec. 26, 1944. H. w. KOST 2,366,114

METHOD OF FORMING SCREW-RECEIVING FASTENERS Original Filed Jan. 31: 1942 1Y0 zvZa WKoHLZ' NVENTOR.

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A TTORNE Y UNITED STATES PATENT OFFICE METHOD OF FORMING SCREW-RECEIVING FASTENERS Harold W. Kost, Birmingham, Mich., assignor to Detroit Harvester Company, Detroit, Mich., a corporation of Michigan Original application January 31, 1942, Serial No.

429,030. Divided and this application April 16, 1943, Serial No. 483,231

2 Claims. (01. 29148) This invention relates to fasteners and particularly to the method of forming fastening devices of sheet material such as sheet metal, such devices being adapted to receive a screw-threaded threads of the screw toward the root thereof. It

will be understood that the steps above described are carried out by dies andiin the final step Z, the

dies are so designed as to remove sharp burrs and to insure that the corners at the upper end of the member. 5 slot are rounded to prevent cutting into the An object is to produce a new and improved threads of the screw; method of forming a fastening device of the above In the final step in forming the fastener shown character whereby the screw thread receiving in Figure 3, the strip'is severed transversely in V aperture is more nearl round so that when the about the region 58 and then bent to form an screw is tightened, the fastener will bite into the upper arm 59 and a lower arm- 50. It willbe root of the thread substantially throughout its observed thatthe advanced edge of the strip is circumference and thereby a more secure and recurved upwardly as indicated at 6! to facilitate in liable connection or fastening i effected. the application of the fastener as will be readily Another object is to produce a method of formunderstood. Inthis fastener it will be manifest ing fasteners of the above character which lends that the finally developed hole is round with the itself particularly to large scale production and edge wall thereof disposed at substantially right insures themanufacture more uniformly of satisangles to the plane of the sheet or striD- D116 factory fasteners. to the thinness of the metal and the method of Other objects and advantages of the invention forming the fastener, it is particularly adapted reside in the particular steps and sequence of to receive machine screws. steps hereinafter more fully described and for It will be manifest from the'above description purposes of illustration but not of limitation, an that these fasteners may be produced speedily embodiment of the invention is shown on the acand at a relatively low cost. The method is parp y g drawing in which ticularly adapted for large volume production in Figure 1 is a top plan view of a sheet metal which many thousands of these fasteners can be strip showing in sequence the three steps emproduced daily. The steps are so designed that ployed in the production of a fastener which is fasteners can be produced of substantially uniparticularly adapted to receive machine screws; form character, each fastener being virtually i ure 2 is a longitudinal sectional view of the identical with the one previousl formed. It is to fastener strip shown on Figure 1; and be understood that the invention is not limited to Figure 3 is an enlarged longitudinal ectional the productiorr of a fastener such as illustrated view of a fastener as ultimately produced from on Figure 3, inasmuch as it may assume numerthe t p according to ures 1 and 2, the same ous other forms depending upon the use for which bei pp i d to a pporting p nel 'to which the fasteneris intended. another Panel is e e y a Screw passing This application constitutes a division'of my through aligned openings in the panels. co-pending application Serial No. 429,030, entitled The illustrated embodiment of the invention Method of forming fastening devices. comprises a strip 53 of sheet metal or other suit- It is to be understood that numerous changes able sheet material on which are illustrated forms i the choice of materials and operation may be 1 Y nd Z which Show successive steps empl y 40 effected without departing from the spirit of the in the manufacture of the fastening device. In n t n especially as defined inthe appended the step X, a protuberance 54 has upwardly slopclaims. I ing sides, a round hole 55 in the central portion WhatI claim is: x v thereof and a slit 55 extending from the hole 55 1, In th meth d of forming a sheet metal t0 the base of the p n t e fo Y structure or element for self-locking engagement which is the next succeeding step, the slot 56' is by a, r w th steps which comprise pressing a nl r ed as also the hole Likewise the side dome-like protuberance out of the normal plane 51 0f the i is Pressed downwardly to of the sheet and at the same time punching out the plane of the strip 53 thereby to form the a und hole in the top of the protuberance and edge of the hole 55' into the form of a helix. punching out a slit extending radially from the In the final operation as exemplified by form Z. round hole to the base of the protuberance, u s the size of the hole 55" is slightl reduced, the quently enlarging the slit and pressing the metal metal at the edge of the hole being thinned at one side of the slit in a direction toward the slightly in order to extend well between the 55 sheet and enlarging the hole substantially to v roundness in plan view so that a portion of the wall 01' the opening is formed into the inner or lower portion of a helix which extends progressively and uniformly to the outer or higher portion of the helix, and subsequently reducing the thickness of metal at the edge of the hole as well as the size of the developed hole to provide a. thread.

2. In the method of forming a fastening device for self-locking engagement by a screw the steps which comprise: providing relatively thin sheet material thicker than the finished thread in engaging portions, pressing a dome like protuberance out of the normal plane of the material and simultaneously punching out around hole in the top of the protuberance as wellas punching out a slit extending radially from the round hole to the base of the protuberance, enlarging both the slit and the hole, pressing the metal at one side of the slit in a direction toward the sheet so that the edge portion of the opening is formed into a helix extending progressively and uniforml from the lower portion to the higher portion of the helix, and pressing the sheet material in the region of the thread engaging edge portion of the hole thereby to reduce the thickness of the material in that region and also to reduce the size of the developed hole and removing the burrs and rounding the corners of the slot.

HAROLD W. KOST. 

